Typically a digital subscriber line (DSL) network comprises a plurality of customer premise equipment (CPE) devices connected to a digital subscriber line access multiplexer (DSLAM) via a bundle of twisted-pair wires for providing broadband service. FIG. 1 illustrates a prior art DSL network. The DSLAM is also connected to a network for sending and receiving data to and from the respective CPE devices. The DSLAM may further be connected to other devices, such as routers, for directing and switching data through the DSL network. A DSLAM comprises a plurality of DSL modems which may be implemented in software residing on one or more digital signals processors (DSP). The customer premise equipment may include a variety of devices such as modems and handsets. By way of example the customer premise equipment of FIG. 1 comprise DSL modems capable of communicating with the DSLAM. The DSLAM may be located, for example, in a central office (CO).
Each of the N CPE DSL modems of FIG. 1 are connected directly to a respective DSL modem in the DSLAM via a dedicated twisted-pair conductor, or POTS (plain old telephone service) line. The twisted-pair conductors are usually part of the public switched telephone network (PSTN). Typically these lines are supplied in bundles of 25 twisted-pair conductors per bundle. There may be greater or fewer twisted-pair conductors per bundle. For example, a typical DSLAM may supply DSL service at VDSL data rates to 25 DSL modems located at the customer end. VDSL data rates are up to 26 Mbps (megabits per seconds) upstream and downstream. Other forms of DSL service having different data rates may also be supplied such as ADSL (up to 1.5 Mbps upstream, 8 Mbps downstream), SHDSL (up to 4 Mbps upstream and downstream), and HDSL (1.5 Mbps upstream and downstream).
High speed dedicated DSL service as described above has many disadvantages. For example, with 25 DSL modems at the customer end, and with each dedicated line capable of carrying data at a rate of 1.5 Mbps, the DSLAM must be able to process data at a rate of 37.5 Mbps. Such high data rate requirements typically require a pool of high speed, and expensive digital signal processors. In addition to the expense, the large number of high speed digital signal processors require large amounts of power, which is frequently in short supply at some of the remote locations that the DSLAMs may be located in.
Furthermore, while dedicated DSL service is supplied to the customer, it is often not needed. Most customer's DSL modems sit idle through much of the day and night. For example, for the most part the customer's DSL modem is not being used while the customer is away at work, or asleep. This represents the majority of the day, even for heavy home computer users. Additionally, even when a customer is using their computer and DSL modem, the DSL communications tend to be bursty. That is, a user might need or want a large amount of bandwidth to download or upload files, but once the file transfers have completed the DSL line servicing the customer might carry only a small amount of data for comparatively long periods of time while the customer uses their computer to view files, write letter, and the like.
Even if customers desire broadband service, many customers may not be able to receive such service as they may be located too far away from the central office that houses the DSLAM. Moving the DSLAM closer to the customers is often impractical or impossible for many reasons, among them being that the electricity required to power the DSLAM may be insufficient in the new location, and running additional power to the new location may be prohibitively expensive.
In such cases, customers may use other forms of communication, namely analog modems. A bank of analog modems may be placed at the central office, often alongside the DSLAM, to provide analog modem service such as ITU-T V.90 service. These analog modems while providing lower speed data service than DSL, are able to operate over longer distances than DSL. Unfortunately, along with occupying a lot of space, which is often in short supply in a central office, banks of analog modems share many of the space and power problems as banks of DSL modems.